Techniques for controlling specific absorption rate of radio energy transmission

ABSTRACT

The disclosure relates to techniques for controlling Specific Absorption Rate (SAR) of radio energy transmission. In particular, the disclosure relates to a radio device and a method for controlling radio energy transmission of a plurality of radio entities to comply with a predefined SAR requirement. Such a radio device includes: a plurality of radio entities configured to transmit radio energy; and a controller configured to control the radio energy transmission of the plurality of radio entities to comply with a predefined Specific Absorption Rate, SAR, requirement, wherein the controller is configured to enable at least two radio entities of the plurality of radio entities operating concurrently based on a shared SAR transmission power restriction which allows the at least two radio entities transmitting concurrently at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. The disclosure further relates to a method for dynamic management of a SAR budget across multiple radio entities.

FIELD

The disclosure relates to techniques for controlling Specific AbsorptionRate (SAR) of radio energy transmission. In particular, the disclosurerelates to a radio device and a method for controlling radio energytransmission of a plurality of radio entities to comply with apredefined SAR requirement. The disclosure further relates to a methodfor dynamic management of a SAR budget across multiple radio entities.

BACKGROUND

SAR—Specific Absorption Rate, is a measure of the amount of RF energyabsorbed by the body when using a mobile device such a phone or atablet. In order to comply with SAR requirements a restriction (e.g. abackoff or another kind of reduction) shall be applied on the maximal TXpower permitted for a specific radio of the device. Note that the SARrequirement is for the maximum allowed transmission (Tx) power; abackoff is one way to relate to this restriction in the context ofbackoff from maximum (HW supported) Tx power. Other ways to relate tothis restriction are applicable as well. When the device has an antennacapable of transmitting concurrently at multiple frequency bands or ifit has multiple radios that emit energy in close physical proximity suchthat the SAR restriction is applied on all of them together anadditional backoff must be taken on the TX power of each radio entity.The resulting TX power from all applied backoffs degrades the wirelessperformance for each participating radio. The disclosure presents asolution to the above described problem.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description.

FIG. 1 is a schematic diagram illustrating RF energy absorption by ahuman body 101 and a SAR restriction 112.

FIG. 2 is a block diagram illustrating a radio device 200 with aplurality of radio entities 201, 202, 203 according to the disclosure.

FIG. 3 is a schematic diagram illustrating a first method 300 formanaging the SAR budget according to the disclosure.

FIG. 4 is a schematic diagram illustrating a second method 400 formanaging the SAR budget according to the disclosure.

FIG. 5 is a time diagram 500 illustrating measurement points used in athird method for managing the SAR budget according to the disclosure.

FIG. 6 is a block diagram illustrating a hardware circuit 600 forcontrolling concurrent radio energy transmissions according to thedisclosure.

FIG. 7 is a schematic diagram illustrating a method 700 for controllingradio energy transmissions according to the disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part thereof, and in which is shownby way of illustration specific aspects in which the invention may bepracticed. It is understood that other aspects may be utilized andstructural or logical changes may be made without departing from thescope of the present invention. The following detailed description,therefore, is not to be taken in a limiting sense, and the scope of thepresent invention is defined by the appended claims.

The following terms, abbreviations and notations will be used herein:

-   -   SAR: Specific Absorption Rate    -   TX: Transmission    -   AQ: Assigned Quota    -   UQ: Unused Quota    -   CQ: Cumulative Quota    -   LQ: Link Quality    -   SA: Stand-Alone mode    -   SH: Shared Transmission mode    -   AP: Activity Percentage    -   AF: Activity Factor    -   CDB: Concurrent Dual Band    -   MA: Moving Average    -   RF: Radio Frequency

It is understood that comments made in connection with a describedmethod may also hold true for a corresponding device configured toperform the method and vice versa. For example, if a specific methodstep is described, a corresponding device may include a unit to performthe described method step, even if such a unit is not explicitlydescribed or illustrated in the figures. Further, it is understood thatthe features of the various exemplary aspects described herein may becombined with each other, unless specifically noted otherwise.

The techniques described herein may be implemented in wirelesscommunication networks, in particular communication networks based onmobile communication standards such as LTE, in particular LTE-A and/orOFDM and successor standards such as 5G. The methods are also applicablefor high speed communication standards from the IEEE 802.11 family, e.g.802.11ac, ax, ad and future IEEE 802.11 amendments. The methods arefurther applicable to on-device radio transmitters compliant to ordesigned in accordance with other wireless standards such as IEEE802.15, the Bluetooth Special Interest Group, or even proprietarywireless transmitter specifications. The methods and devices describedbelow may be implemented in electronic devices such as cellularhandsets, Tablets, Laptops, and mobile or wireless devices. Note thatSAR is particularly relevant for devices held in proximity to the bodysuch as cellular handsets, Tablets, Laptops, and mobile or wirelessdevices but less relevant to infrastructure devices such as accesspoints or base stations as they are not held in proximity to the body.The described devices may include integrated circuits and/or passivesand may be manufactured according to various technologies. For example,the circuits may be designed as logic integrated circuits, analogintegrated circuits, mixed signal integrated circuits, optical circuits,memory circuits and/or integrated passives.

In the following, radio frequency (RF) signals and transmission of radioenergy are described. Radio signals may be or may include radiofrequency signals radiated by a radio transmitting device (referredhereinafter as a radio device or a radio entity) with a radio frequencylying in a range of about 3 kHz to about 300 GHz. The frequency rangemay correspond to frequencies of alternating current electrical signalsused to produce and detect radio waves.

In the following, embodiments are described with reference to thedrawings, wherein like reference numerals are generally utilized torefer to like elements throughout. In the following description, forpurposes of explanation, numerous specific details are set forth inorder to provide a thorough understanding of one or more aspects ofembodiments. However, it may be evident to a person skilled in the artthat one or more aspects of the embodiments may be practiced with alesser degree of these specific details. The following description istherefore not to be taken in a limiting sense.

The various aspects summarized may be embodied in various forms. Thefollowing description shows by way of illustration various combinationsand configurations in which the aspects may be practiced. It isunderstood that the described aspects and/or embodiments are merelyexamples, and that other aspects and/or embodiments may be utilized andstructural and functional modifications may be made without departingfrom the scope of the present disclosure.

FIG. 1 is a schematic diagram 100 illustrating RF energy absorption by ahuman body 101 and a SAR restriction 112. SAR—Specific Absorption Rate,is a measure of the amount of RF energy 111 absorbed by the body 101when using a mobile device 110 such as a phone or a tablet. In order tocomply with SAR requirements a restriction 112 (backoff) shall beapplied on the maximal TX power permitted for a specific radio of thedevice 110. Note that the SAR requirement is for the maximum allowedtransmission (Tx) power; a backoff is one way to relate to thisrestriction in the context of backoff from maximum (HW supported) Txpower. Other ways to relate to this restriction are applicable as well.When the device 110 has an antenna capable of transmitting concurrentlyat multiple frequency bands or if it has multiple radios that emitenergy 111 in close physical proximity such that the SAR restriction 112is applied on all of them together an additional backoff must be takenon the TX power of each radio entity. The resulting TX power from allapplied backoffs yields a poor wireless performance for eachparticipating radio.

Existing SAR solutions derive a fixed worst-case backoff value per eachradio/band where that backoff needs to account for the case where allradios are transmitting concurrently. Alternatively, existing solutionsshall forbid any concurrency between multiple radio technologies underSAR constraints.

Since the worst-case backoff will be applied by the radio entityregardless of the level of activity of other wireless technologies, thismay result in an unnecessarily poor wireless performance. As an example,if a radio is permitted to transmit at 19 dBm, and needs to reduce itsTX power to 15 dBm under SAR constraint 112, then if that radio couldalso participate in a Concurrent Dual Band (CDB) scenario it would needto apply an additional backoff of up to 3 dB resulting in TX power of 12dBm applied on all its transmissions—this may cause a severe rangeproblem. Alternatively, if TX concurrency between multiple radios isprohibited severe degradation in user experience may result.

FIG. 2 is a block diagram illustrating a radio device 200 with aplurality of radio entities 201, 202, 203 according to the disclosure.

The radio device 200 comprises a plurality of radio entities 201, 202,203 configured to transmit radio energy 211, 212, 213. The radio device200 further comprises a controller 210 that is configured to control theradio energy 211, 212, 213 transmission of the plurality of radioentities 201, 202, 203 to comply with a predefined Specific AbsorptionRate, SAR, requirement. The controller 210 is further configured toenable at least two radio entities (e.g. 201, 202) of the plurality ofradio entities operating concurrently based on a shared SAR transmissionpower restriction which allows the at least two radio entitiestransmitting concurrently at a predefined duty cycle, e.g. at 100% dutycycle, without violating the SAR requirement.

The controller 210 may further be configured to enable at least oneradio entity (e.g. 201) of the plurality of radio entities operating instand-alone mode based on a stand-alone SAR transmission powerrestriction which allows the at least one radio entity transmitting at apredefined duty cycle, e.g. at 100% duty cycle, without violating theSAR requirement.

Thus, the radio device may operate in a first mode where two or moreradio entities operate concurrently and where the shared SARtransmission power restriction is fulfilled; and the radio device mayoperate in a second mode where each radio entity operates in stand-alonemode where the stand-alone SAR transmission power restriction isfulfilled for each radio entity.

The shared SAR transmission power restriction may be based on a SARbudgeting scheme. The shared SAR transmission power restriction may beconfigured to restrict transmission times of the at least two radioentities within a specific time window to predefined quotas, e.g. asdescribed below with respect to FIGS. 3 to 5 in more detail. Thepredefined quotas may be specified as percentage values of the specifictime window. The specific time window may be less than a period overwhich the SAR requirement is defined.

The controller 210 may be configured to assign time quotas to theplurality of radio entities over a single time window, e.g. as describedbelow with respect to FIGS. 3 to 5 in more detail. Alternatively, thecontroller 210 may be configured to assign time quotas to the pluralityof radio entities over multiple time windows, e.g. as described belowwith respect to FIGS. 3 to 5 in more detail.

Alternatively, the controller 210 may be configured to assigntransmission power quotas to the plurality of radio entities 201, 202,203, e.g. as described below with respect to FIG. 5 in more detail. Thecontroller 210 may be configured to assign the transmission power quotasbased on a moving average filter, e.g. as described below with respectto FIG. 5 in more detail.

The controller 210 may be configured to apply a strict duty cyclingscheme in which within a specific period each transmission is followedby a quiet period to guarantee the predefined duty cycle.

The controller 210 may be configured to apply a flexible quota scheme inwhich for a given time window and a given quota a cumulativetransmission time within the time window shall not exceed a threshold.The threshold may be a function of the quota and the time window, inparticular a product of the quota and the time window, e.g. as describedbelow with respect to FIGS. 3 to 5 in more detail.

The controller 210 may be configured to enable a radio entity of theplurality of radio entities 201, 202, 203 increasing its transmissionpower to a power level above a given stand-alone SAR transmission powerrestriction when the radio entity is correspondingly decreasing itstransmission power thereafter to fulfill the standalone SAR transmissionpower restriction within a given time window. The power level maycorrespond to the standalone SAR transmission power restriction dividedby an activity percentage of the radio entity within the time window,e.g. as described below with respect to FIGS. 3 to 5 in more detail.

The controller 210 may be configured to control the energy transmissionof the plurality of radio entities 201, 202, 203 based on averaging overactivities of the plurality of radio entities within a measurementwindow, e.g. as described below with respect to FIGS. 3 to 5 in moredetail.

The controller 210 may be configured to allow overlapping activities ofthe at least two radio entities as long as a cumulative activity acrossall radio entities 201, 202, 203 of the plurality of radio entities isbelow a threshold within a measurement window.

In the following an exemplary solution implemented by the controller 210is described in more detail. The solution is based on allocating a quotaof TX activity for each participating radio (entity) 201, 202, 203 thatis applicable within a specific time window. A quota defines an energybudget (Power×Time) for the radio 201, 202, 203 over that window. Usingsmart management of quota allocation over consecutive windows and orsliding windows allows achieving an optimal solution that does notsacrifice TX power while still fully complying with SAR requirements.

The solution allows customers to operate multiple radio technologiesconcurrently over the same SAR antenna without requiring an additionalbackoff on the TX power of each radio due to this concurrency andwithout severe restrictions on the timing of TX operations. This becomespossible by leveraging the sporadic nature of TX traffic as well as themethod in which SAR is being measured. Note that the SAR requirement isfor the maximum allowed transmission (Tx) power; a backoff is one way torelate to this restriction in the context of backoff from maximum (HWsupported) Tx power. Other ways to relate to this restriction areapplicable as well.

Such capability is of special interest for SAR-constrained CDB(Concurrent Dual Band) solutions as well as WLAN+LAA sharing solutionswhich shall become important technologies to support in wirelessproducts in the next years.

Depending on the Device Form-Factor SAR measurement and budgeting iseither performed on each antenna separately or on multiple antennastogether. The solution is applicable to both cases. An example forsingle antenna is when WIFI 2.4 GHz Band and WIFI 5 GHz Band aretransmitting over the same antenna. An example for more than one antennais when multiple antennas on the device are in close physical proximitysuch that a single SAR constraint is applicable to all. Other examplesare WIFI 5 GHz and LAA (License Assisted Access—i.e. LTE within 5 GHzBand) radios that may share the same antenna or WIFI 2.4 GHz andBluetooth.

In order to participate in SAR budgeting scheme each radio entity 201,202, 203 shall support a method to restrict its transmission time and orpower within a specific time window to a pre-defined quota specified asa percentage of that window. In order to comply with the allocatedquota, the radio entity 201, 202, 203 may deploy either a strict dutycycling scheme in which within a specific period each transmission isfollowed by a quiet period that guarantees a predefined duty cycle (e.g.N msec of TX is followed by 2N msec of quiet time to guarantee a dutycycle of N/(N+2N)=33.3%) or it may be able to deploy a more flexiblequota scheme based on a TX counter in which for any given quota (e.g.Q=30%) and a Time Window (e.g. T=100 ms) the cumulative transmissiontime of the radio within that time window shall not exceed Q*T (30 ms).

In general, each radio (entity) 201, 202, 203 shall be assigned with aSAR TX power restriction that is applicable when the radio is operatingin Stand-Alone mode (SA_SAR_POWER) and another Shared SAR TX powerrestriction that is applicable when all radio-entities are operatingconcurrently (SH_SAR_POWER).

The SA_SAR_POWER restriction allows a single radio (e.g. 201) totransmit at 100% duty-cycle without violating SAR. Like-wise, theSH_SAR_POWER restriction allows all radio entities 201, 202, 203 totransmit concurrently at 100% duty-cycle without violating SAR.

By leveraging the physical nature of SAR and the way it is measured itcan be observed that a radio may increase its TX power beyondSA_SAR_POWER and still comply with SAR as long it proportionallydecreases its activity time within the measurement window. In otherwords, let AP be the Activity Percentage within a window with values inthe range [0 . . . 1], then a radio may transmit at a Power value ofSA_SAR_POWER/AP within that window without violating SAR—as long as thewindow size is small enough (i.e. significantly smaller than the SARmeasurement period).

This idea can be scaled for multiple radios case by averaging theactivity of multiple radios within a measurement window. Since any radiohas an SA_SAR_POWER that guarantee SAR compliancy with 100% duty cyclealso any superposition of radio activities (Radio A is active for X msecthen radio B is active for Y msec) is compliant with SAR. Due to thephysical nature of SAR it can also be claimed that the activity periodsof the multiple radio can overlap without violating SAR as long as thecumulative activity across all radios 201, 202, 203 within the window isbelow or equal to 100%. Such an overlap may create a temporal crossingof the maximum allowed cumulative TX power, however since SAR ismeasured over a period which is longer than the time window in practiceno SAR violation occurs.

Several mechanisms are introduced in the following with respect to FIGS.3 to 7 to leverage the above observations. Using centralized radiomanagement (central controller 210) a method can be formed that allowsoptimizing the TX power of all radio entities 201, 202, 203 based ontheir specific requirements while complying with the overall SAR budgetof the system.

The central controller 210 can track TX activity 211, 212, 213 of eachradio 201, 202, 203 as well as the Link Quality of each radio 201, 202,203 and make allocation decisions based on that information. LinkQuality can be defined either as the success rate for sending TX packetsover a period of time as tracked by the packet acknowledge rate or asusing another approximation such as the MCS that the radio is using(lower MCS indicates lower link quality).

The controller 210 can use one of the methods described in the followingwith respect to FIGS. 3 to 5 to manage the SAR budget.

FIG. 3 is a schematic diagram illustrating a first method 300 formanaging the SAR budget according to the disclosure. This first methodis related to managing Time Quota over single window. An exemplarynumber of two radio entities (denoted A and B, e.g. corresponding to 201and 202 in FIG. 2 ) is illustrated which produce Radio A activity 301and Radio B activity 302. A and B may also specify different frequencybands in which two radio entities transmit radio energy. FIG. 3 depictsRadio A activity 301, Radio B activity 302, Cumulative Activity 303,Radio A Quota 304, Radio B Quota 305 in different time intervals (ortime windows) 310, 320, 330, 340.

In this method 300 each radio entity is assigned with a Quota Qi (seeRadio A Quota 304 and Radio B Quota 305 in FIG. 3 ) for performingtransmissions within a time window, specified as a percentage of theWindow's Time duration WT. The radio can manage the budget byinitializing a counter to the value Qi*WT when the window starts thendecrementing the counter by the TX Time TT of each packet. Packettransmission is permissible only if counter value is bigger than TT. Theradio may either exhaust all its quota or only a portion of it. At theend of the window the central controller (e.g. controller 210 depictedin FIG. 2 ) will capture the remaining budget in all counters of allradios and adjust the Quota for next window according to the algorithmspecified below. An example algorithm that may be used by the centralcontroller to allocate Quota:

-   -   1. Assigned Quotas for all radios (AQi) is always allocated such        that Σ(AQi)=<100%.    -   2. Initially Quota is split evenly among the radios (e.g.        AQ1=50%, AQ2=50%)    -   3. After one window is over the controller will collect the        following information from each radio:        -   a. Unused Quota (UQ)—the remaining quota upon end of window        -   b. Link Quality—as defined above    -   4. If ΣUQi>0:        -   a. If all radios have UQi>0—no change in quotas.        -   b. If some radios (e.g. radio 1) have UQi=0 and other radios            (e.g. radio 2) have UQi>0: decrease the quota of radio 2 by            50%*UQ2 and increase the quota of radio 1 by the same            amount.    -   5. Otherwise (ΣUQi=0):        -   a. the controller will check if current quotas should be            adjusted using the following algorithm:            -   i. If there is a radio with AQi<(100%/num_of_radios) and                LQ<Thresh set AQi=(100%/num_of_radios) for that radio                and decrease the AQ of all other radios accordingly.            -   ii. The above will allow radios that are not getting a                fair share of the quota and suffer from low Link Quality                to gain back their share.    -   6. Repeat

Using Method1 all radios can continue transmitting using SA_SAR_POWERand need not suffer the additional power backoff implied bySH_SAR_POWER.

The diagram in FIG. 3 depicts a sequence in which Method 1 is applied tomanage the quota of two Bands. Since Band B does not use its quota thecentral controller gradually increases the allocated quota for Radio A.

FIG. 4 is a schematic diagram illustrating a second method 400 formanaging the SAR budget according to the disclosure. This second methodis related to managing Time Quota over multiple windows. An exemplarynumber of two radio entities (denoted A and B, e.g. corresponding to 201and 202 in FIG. 2 ) is illustrated which produce Radio A activity 301and Radio B activity 302. A and B may also specify different frequencybands in which two radio entities transmit radio energy. FIG. 4 depictsRadio A activity 401, Radio B activity 402, Cumulative Activity 403,Band A Limit 404, Band B Limit 405 in different time intervals (or timewindows) 410, 420, 430, 440, 450, 460.

Method 2 describes an optimized version of Method 1 (shown in FIG. 3 )working in window-pairs—where on the first window 410 each radio shallbe assigned with an “unrestricted quota” of 100% and on the next window420 an adjustment is done to compensate for any budget violationsoccurring on previous window 410. The advantage of this version is thatit does not restrict in advance the quota of each radio while stillcomplying with the overall SAR budget measured across the two windows.

The diagram shown in FIG. 4 depicts the flow when Method 2 is used. Ascan be seen on the first window 410 each band is assigned with a quotaof 100%. During the window period the cumulative activity 403 of bothbands is 150%—in order to compensate for that, on the second window 420the cumulative budget 403 is dropped to 50% (split evenly among the twobands) hence no violation is observed when measuring SAR over the twowindows 410, 420. On the next window 430 the budget is again 100% perband—and since each band uses its entire budget it drops to 0% on thenext window 440.

In practice this method allows both bands to transmit freely within eachwindow with no quota enforcement as long as their cumulative activity403 does not cross 100%.

With Method 2, the central controller (e.g. controller 210) can use thefollowing exemplary algorithm to allocate quotas for each window:

-   -   1. For window1:        -   a. Assign a quota of 100% for each radio        -   b. After window1 is over collect the following information            from each radio:            -   i. Link Quality (LQ)—as defined above            -   ii. Activity Factor (AF)—this is the activity rate                during window 1—calculated as TX Time/Window Time    -   2. For window2:        -   a. Calculate Cumulative Quota (CQ) for window2 as:

CQ=200%−ΣAFi

-   -   -   b. Allocate an Activity Quota for each radio under the            constraint that Σ(AQi)=CQ using one of the following            methods:            -   i. Symmetric allocation—the remaining quota is split                evenly among the radios: AQi=(1/num_of_radios)*CQ            -   ii. Proportional allocation—the remaining quota is split                such that radios with higher activity receive higher                quota on next window: AQi=(AFi/ΣAFi)*CQ            -   iii. Link Quality based allocation—the remaining quota                shall be split such that radios with a lower Link                Quality shall receive a higher quota while keeping the                constraint that Σ(AQi)=CQ.

    -   3. Repeat

An optimization that can be applied to Method 2 is for the algorithm toperform the averaging over more than 2 windows in order to smooth thetraffic pattern. For example, averaging over 3 windows will guaranteethat there is never a single window during which no TX is allowed.

FIG. 5 is a time diagram 500 illustrating measurement points used in athird method for managing the SAR budget according to the disclosure.This third method is related to managing TX Power Quota using MovingAverage Filter. An exemplary number of two radio entities (denoted Radio1 and Radio 2, e.g. corresponding to 201 and 202 in FIG. 2 ) isillustrated. FIG. 4 depicts TX time 510 for Radio 1 and TX time 520 forRadio 2. For Radio 2 different exemplary measurement samples 501, 502,503, 504, 505 are illustrated during a requested TX duration 521 forwhich TX power shall be defined by the highest measurement sample.

Method 3 describes a different method to ensure that the total averageTX power over any window of length t_(w) does not surpass the SARbudget. This method is based on tracking the Moving Average (MA) of thecumulative TX power of all participating radios over a window of sizet_(w).

Method 3 applies the dynamic SAR restriction on the TX power rather thanthe transmission time. Tracking the cumulative TX power of all radiosover a relevancy window is done using an MA (Moving Average) filter thatestimates the effective SAR due to the radio transmissions over time. Inthis scheme, the controller (e.g. controller 210 depicted in FIG. 2 )measures the TX power of each radio during short time intervals(t_(m)—measurement interval, e.g. 100 uSec) and continuously calculatesthe effective SAR using a Moving Average filter such as:

SAR_POWER[n]=(1−α)SAR_POWER[n−1]+αΣTXi[n];

with α set to be t_(m)/t_(w), where t_(m) is the measurement interval,and t_(w) is the time window. ΣTXi[n] is the sum of average TX power ofall radios during current the current (n-y) t_(m) measurement window.

While the filter equation above is a 1^(st) order ARMA (IIR) filter, theSAR POWER value can be calculated using as a FIR MA filter or as an IIRARMA filter.

The device shall restrict the power of new transmissions to comply withthe SAR budget across t_(w) as follows: For any new transmissionrequest, the controller shall set the allowed TX power for it in a waythat guarantees that the resulting SAR in any time window of lengtht_(w) containing the transmission does not surpass the allowed quota.

The central controller shall maintain a list of all active transmittingradios, with their specific max TX power, TX start time and TX durationand will calculate the allocated TX power for a new transmission thatstarts at time to using the following formula:

Let_ESTIMATED_SAR(t) be SAR_POWER(t), where t is a number in the range{t ₀ , t ₀+min(t _(w), requested_tx_duration}, in increments of t _(m).

Then max TX power allowed for the new transmission will be calculatedas:

MAX_TX_POWER=Min{t as defined above, (MAX_SAR−ESTIMATED_SAR(t))},

where MAX_SAR is the maximal allowed cumulative TX Power for allparticipating radios that guarantees no violation of the SAR budget.

The diagram shown in FIG. 6 illustrates an example of the measurementpoints 501, 502, 503, 504, 505 that will be used for resolving the MaxTX power in method 3:

Method 1 (shown in FIG. 3 ) and Method 2 (shown in FIG. 4 ) imply thatthere are periods during which both radios transmit concurrently usingtheir SA_POWER rather than their SH_POWER. While this temporal violationis compensated over the measurement window, some regulatory bodies mayrequire a restriction on the maximal period where such concurrency ispermitted. The HW circuit 600 shown in FIG. 6 can be used forrestricting the maximal amount of concurrency within a given measurementwindow.

FIG. 6 is a block diagram illustrating a hardware circuit 600 forcontrolling concurrent radio energy transmissions according to thedisclosure. The hardware circuit 600 can be used for Quota allocationwith hardware restriction of maximal concurrency.

The hardware circuit 600 comprises an exemplary number of two radioentities (Radio A 610 and Radio B 620). The hardware circuit 600comprises a concurrency detection circuit 620 in which a concurrencycounter 632 is implemented which counts concurrent transmissions ofradio A and Radio B. A maximum allowed concurrency value 634 can beloaded 633 to counter 632 which forms a threshold for the counter 632.An AND gate 631 passes concurrent transmissions of both radios 610, 620to the counter 632. The transmissions of each radio 610, 620 aremeasured after the MAC 612, 622 of each radio entity 610, 620 and beforetransmitter 611, 621. If counter 632 is greater zero, concurrency isallowed 635 which is signaled to TX arbitration circuit 640. TXarbitration circuit includes a concurrency control block 642 whichdetects if both bands are transmitting and concurrency is not allowed.If this condition is fulfilled, the transmission of the band with lowerpriority is killed. Priorities are determined by band priority block641.

The hardware circuit 600 can be implemented in a radio device, e.g. aradio device 200 described above with respect to FIG. 2 . The radiodevice comprises a plurality of radio entities 610, 620 (e.g.corresponding to entities 201, 202, 203 in FIG. 2 ) configured totransmit radio energy, e.g. as described above with respect to FIGS. 1to 5 . The radio device includes a concurrency detection circuit 620configured to detect concurrent transmissions of at least two radioentities of the plurality of radio entities 610, 620. The radio devicefurther includes a transmission arbitration circuit 640 configured todisable transmission of at least one radio entity of the at least twoconcurrently transmitting radio entities based on a concurrencycriterion 642.

The concurrency criterion 642 may be based on a Specific AbsorptionRate, SAR, requirement. The concurrency detection circuit 620 may beconfigured to count concurrent transmissions of the at least two radioentities 610, 620 within a measurement interval. The concurrencydetection circuit 620 may be configured to indicate a concurrencyallowance 635 to the transmission arbitration circuit 640 if the countedconcurrent transmissions are below a threshold.

The transmission arbitration circuit 640 may be configured to disabletransmission of the at least one radio entity of the at least twoconcurrently transmitting radio entities if the concurrency detectioncircuit 620 stops indicating concurrency allowance 635.

The transmission arbitration circuit 640 may be configured to disabletransmission of the at least one radio entity of the at least twoconcurrently transmitting radio entities based on priorities 641 of theat least two concurrently transmitting radio entities 610, 620. Thepriorities 641 may be based on strict priority to one of the radioentities 610, 620, strict priority based on access category and/or RoundRobin between the radio entities 610, 620.

In the following a functionality of the hardware circuit 600 isdescribed in more detail. At the beginning of each window a counter 632is initialized to the max time allowed for concurrent transmissionwithin that window (MAX_ALLOWED_CONCURRENCY). During the window, counter632 is decremented whenever both radios 610, 620 are transmitting ineach tick. Once counter 632 is reaching zero an arbitration logic 640 isarmed. The arbitration logic 640 will kill the transmission of the radiowith the lower priority whenever the other radio is active. The priority641 can be defined as either strict priority to one of the bands, strictpriority based on Access Category or Round Robin with between the twobands per TX packet.

By controlling the value of MAX_ALLOWED_CONCURRENCY the behavior istuned to be either a real-TDM between the radios (zero concurrency),full concurrency or a hybrid mode of operation in which quotas areenforced within the window while he overall concurrency time isrestricted.

Since Method 3 (described above with respect to FIG. 5 ) makes TX powerdecisions one at a time, it may be that a high priority TX request mayrequire a TX power higher than permitted by the method. In this case,the central controller may use the HW circuit 600 described above to“kill” a lower priority TX activity such that its power budget may thenbe assigned to the high priority TX request. It should be noted that forMethod 3, the central controller may be provided in advance the inputsregarding any pre-assigned Tx activity on any of the radios, to allowfor a “forecasting” calculation of allowed Tx powers, to comply with theSAR requirements.

FIG. 7 is a schematic diagram illustrating a method 700 for controllingradio energy transmissions according to the disclosure.

The method 700 allows controlling radio energy transmission of aplurality of radio entities, e.g. entities 201, 202, 203 as shown inFIG. 2 or entities 610, 620 as shown in FIG. 6 , to comply with apredefined Specific Absorption Rate, SAR, requirement. The method 700comprises: enabling 701 at least two radio entities of the plurality ofradio entities operating concurrently based on a shared SAR transmissionpower restriction which allows the at least two radio entitiestransmitting concurrently at a predefined duty cycle, in particular at100% duty cycle, without violating the SAR requirement.

The method 700 may further comprise: enabling at least one radio entityof the plurality of radio entities operating in stand-alone mode basedon a stand-alone SAR transmission power restriction which allows the atleast one radio entity transmitting at a predefined duty cycle, inparticular at 100% duty cycle, without violating the SAR requirement.

The shared SAR transmission power restriction may be based on a SARbudgeting scheme.

The method 700 may further comprise: restricting transmission times ofthe at least two radio entities within a specific time window topredefined quotas. The predefined quotas may be specified as percentagevalues of the specific time window. The specific time window may be lessthan a period over which the SAR requirement is defined.

The method 700 may further comprise: assigning time quotas to theplurality of radio entities over a single time window, e.g. as describedabove with respect to FIG. 3 . Alternatively, the method 700 maycomprise: assigning time quotas to the plurality of radio entities overmultiple time windows, e.g. as described above with respect to FIG. 4 .

The devices and systems described in this disclosure may be implementedas Digital Signal Processors (DSP), micro-controllers or any otherside-processor or hardware circuit on a chip or an application specificintegrated circuit (ASIC).

Embodiments described in this disclosure can be implemented in digitalelectronic circuitry, or in computer hardware, firmware, software, or incombinations thereof, e.g. in available hardware of mobile devices or innew hardware dedicated for processing the methods described herein.

The present disclosure also supports a computer program productincluding computer executable code or computer executable instructionsthat, when executed, causes at least one computer to execute theperforming and computing blocks described herein, in particular themethods 300, 400, 500, 700 described above with respect to FIGS. 3 to 5and 7 and the computing blocks described above with respect to FIGS. 2and 6 . Such a computer program product may include a non-transientreadable storage medium storing program code thereon for use by aprocessor, the program code comprising instructions for performing themethods or the computing blocks as described above.

EXAMPLES

The following examples pertain to further embodiments. Example 1 is aradio device, comprising: a plurality of radio entities configured totransmit radio energy; and a controller configured to control the radioenergy transmission of the plurality of radio entities to comply with apredefined Specific Absorption Rate, SAR, requirement, wherein thecontroller is configured to enable at least two radio entities of theplurality of radio entities operating concurrently based on a shared SARtransmission power restriction which allows the at least two radioentities transmitting concurrently at a predefined duty cycle, inparticular at 100% duty cycle, without violating the SAR requirement.

In Example 2, the subject matter of Example 1 can optionally includethat the controller is further configured to enable at least one radioentity of the plurality of radio entities operating in stand-alone modebased on a stand-alone SAR transmission power restriction which allowsthe at least one radio entity transmitting at a predefined duty cycle,in particular at 100% duty cycle, without violating the SAR requirement.

In Example 3, the subject matter of any one of Examples 1-2 canoptionally include that the shared SAR transmission power restriction isbased on a SAR budgeting scheme.

In Example 4, the subject matter of any one of Examples 1-2 canoptionally include that the shared SAR transmission power restriction isconfigured to restrict transmission times of the at least two radioentities within a specific time window to predefined quotas.

In Example 5, the subject matter of Example 4 can optionally includethat the predefined quotas are specified as percentage values of thespecific time window.

In Example 6, the subject matter of Example 4 can optionally includethat the specific time window is less than a period over which the SARrequirement is defined.

In Example 7, the subject matter of Example 4 can optionally includethat the controller is configured to assign time quotas to the pluralityof radio entities over a single time window.

In Example 8, the subject matter of Example 4 can optionally includethat the controller is configured to assign time quotas to the pluralityof radio entities over multiple time windows.

In Example 9, the subject matter of Example 4 can optionally includethat the controller is configured to assign transmission power quotas tothe plurality of radio entities.

In Example 10, the subject matter of Example 9 can optionally includethat the controller is configured to assign the transmission powerquotas based on a moving average filter.

In Example 11, the subject matter of any one of Examples 1-2 canoptionally include that the controller is configured to apply a strictduty cycling scheme in which within a specific period each transmissionis followed by a quiet period to guarantee the predefined duty cycle.

In Example 12, the subject matter of any one of Examples 1-2 canoptionally include that the controller is configured to apply a flexiblequota scheme in which for a given time window and a given quota acumulative transmission time within the time window shall not exceed athreshold.

In Example 13, the subject matter of Example 12 can optionally includethat the threshold is a function of the quota and the time window, inparticular a product of the quota and the time window.

In Example 14, the subject matter of any one of Examples 1-2 canoptionally include that the controller is configured to enable a radioentity of the plurality of radio entities increasing its transmissionpower to a power level above a given stand-alone SAR transmission powerrestriction when the radio entity is correspondingly decreasing itstransmission power thereafter to fulfill the standalone SAR transmissionpower restriction within a given time window.

In Example 15, the subject matter of Example 14 can optionally includethat the power level corresponds to the standalone SAR transmissionpower restriction divided by an activity percentage of the radio entitywithin the time window.

In Example 16, the subject matter of any one of Examples 1-2 canoptionally include that the controller is configured to control theenergy transmission of the plurality of radio entities based onaveraging over activities of the plurality of radio entities within ameasurement window.

In Example 17, the subject matter of any one of Examples 1-2 canoptionally include that the controller is configured to allowoverlapping activities of the at least two radio entities as long as acumulative activity across all radio entities of the plurality of radioentities is below a threshold within a measurement window.

In Example 18, the subject matter of any one of Examples 1-2 canoptionally include that the controller is configured to stop an ongoingtransmission of at least one radio entity in order to allow at leastanother radio entity to commence transmitting and still meeting the SARrequirement.

Example 19 is a radio device, comprising: a plurality of radio entitiesconfigured to transmit radio energy; a concurrency detection circuitconfigured to detect concurrent transmissions of at least two radioentities of the plurality of radio entities; and a transmissionarbitration circuit configured to disable transmission of at least oneradio entity of the at least two concurrently transmitting radioentities based on a concurrency criterion.

In Example 20, the subject matter of Example 19 can optionally includethat the concurrency criterion is based on a Specific Absorption Rate,SAR, requirement.

In Example 21, the subject matter of any one of Examples 19-20 canoptionally include that the concurrency detection circuit is configuredto count concurrent transmissions of the at least two radio entitieswithin a measurement interval.

In Example 22, the subject matter of any one of Examples 19-20 canoptionally include that the concurrency detection circuit is configuredto relate to a Tx power weighted list of concurrent transmissions of theat least two radio entities within a measurement interval.

In Example 23, the subject matter of Example 21 can optionally includethat the concurrency detection circuit is configured to indicate aconcurrency allowance to the transmission arbitration circuit if thecounted concurrent transmissions are below a threshold.

In Example 24, the subject matter of Example 23 can optionally includethat the transmission arbitration circuit is configured to disabletransmission of the at least one radio entity of the at least twoconcurrently transmitting radio entities if the concurrency detectioncircuit stops indicating concurrency allowance.

In Example 25, the subject matter of any one of Examples 19-20 canoptionally include that the transmission arbitration circuit isconfigured to disable transmission of the at least one radio entity ofthe at least two concurrently transmitting radio entities based onpriorities of the at least two concurrently transmitting radio entities.

In Example 26, the subject matter of Example 25 can optionally includethat the priorities are based on strict priority to one of the radioentities, strict priority based on access category and/or Round Robinbetween the radio entities.

Example 27 is a method for controlling radio energy transmission of aplurality of radio entities to comply with a predefined SpecificAbsorption Rate, SAR, requirement, the method comprising: enabling atleast two radio entities of the plurality of radio entities operatingconcurrently based on a shared SAR transmission power restriction whichallows the at least two radio entities transmitting concurrently at apredefined duty cycle, in particular at 100% duty cycle, withoutviolating the SAR requirement.

In Example 28, the subject matter of Example 27 can optionally include:enabling at least one radio entity of the plurality of radio entitiesoperating in stand-alone mode based on a stand-alone SAR transmissionpower restriction which allows the at least one radio entitytransmitting at a predefined duty cycle, in particular at 100% dutycycle, without violating the SAR requirement.

In Example 29, the subject matter of any one of Examples 27-28 canoptionally include that the shared SAR transmission power restriction isbased on a SAR budgeting scheme.

In Example 30, the subject matter of any one of Examples 27-28 canoptionally include: restricting transmission times of the at least tworadio entities within a specific time window to predefined quotas.

In Example 31, the subject matter of Example 30 can optionally includethat the predefined quotas are specified as percentage values of thespecific time window.

In Example 32, the subject matter of Example 30 can optionally includethat the specific time window is less than a period over which the SARrequirement is defined.

In Example 33, the subject matter of Example 30 can optionally include:assigning time quotas to the plurality of radio entities over a singletime window.

In Example 34, the subject matter of Example 30 can optionally include:assigning time quotas to the plurality of radio entities over multipletime windows.

Example 35 is a device for controlling radio energy transmission of aplurality of radio entities to comply with a predefined SpecificAbsorption Rate, SAR, requirement, the device comprising: means forenabling at least two radio entities of the plurality of radio entitiesoperating concurrently based on a shared SAR transmission powerrestriction which allows the at least two radio entities transmittingconcurrently at a predefined duty cycle, in particular at 100% dutycycle, without violating the SAR requirement.

In Example 36, the subject matter of Example 35 can optionally include:means for enabling at least one radio entity of the plurality of radioentities operating in stand-alone mode based on a stand-alone SARtransmission power restriction which allows the at least one radioentity transmitting at a predefined duty cycle, in particular at 100%duty cycle, without violating the SAR requirement.

Example 37 is a radio system, comprising: a plurality of radio entitiesconfigured to transmit radio energy; a concurrency detection circuitconfigured to detect concurrent transmissions of at least two radioentities of the plurality of radio entities; and a transmissionarbitration circuit configured to disable transmission of at least oneradio entity of the at least two concurrently transmitting radioentities based on a concurrency criterion.

In Example 38, the subject matter of Example 37 can optionally includethat the concurrency criterion is based on a Specific Absorption Rate,SAR, requirement.

Example 39 is a computer readable non-transitory medium on whichcomputer instructions are stored which when executed by a computer causethe computer to perform the method of any one of Examples 27 to 34.

In addition, while a particular feature or aspect of the disclosure mayhave been disclosed with respect to only one of several implementations,such feature or aspect may be combined with one or more other featuresor aspects of the other implementations as may be desired andadvantageous for any given or particular application. Furthermore, tothe extent that the terms “include”, “have”, “with”, or other variantsthereof are used in either the detailed description or the claims, suchterms are intended to be inclusive in a manner similar to the term“comprise”. Furthermore, it is understood that aspects of the disclosuremay be implemented in discrete circuits, partially integrated circuitsor fully integrated circuits or programming means. Also, the terms“exemplary”, “for example” and “e.g.” are merely meant as an example,rather than the best or optimal.

Although specific aspects have been illustrated and described herein, itwill be appreciated by those of ordinary skill in the art that a varietyof alternate and/or equivalent implementations may be substituted forthe specific aspects shown and described without departing from thescope of the present disclosure. This application is intended to coverany adaptations or variations of the specific aspects discussed herein.

Although the elements in the following claims are recited in aparticular sequence with corresponding labeling, unless the claimrecitations otherwise imply a particular sequence for implementing someor all of those elements, those elements are not necessarily intended tobe limited to being implemented in that particular sequence.

1. A radio device, comprising: a plurality of radio entities configuredto transmit radio energy; and a controller communicatively coupled tothe plurality of radio entities and configured to: assign first timequotas to the plurality of the radio entities for transmission of radioenergy during a first time window, cause the plurality of radio entitiesto respectively transmit radio energy for first durations less than orequal to the first time quotas, assign second time quotas to theplurality of radio entities for transmission of radio energy during asecond time window based on the first durations and the first timequotas, and cause the plurality of radio entities to transmit radioenergy based on the second time quotas. 2-25. (canceled)
 26. The radiodevice of claim 1, wherein the second time quotas are determined basedon a difference between the first durations and the first time quotas.27. The radio device of claim 1, wherein a sum of the first durationsand the second time quotas is less than or equal to twice a length ofthe first time window.
 28. The radio device of claim 1, wherein thecontroller is further configured to: assign third time quotas to theplurality of radio entities for transmission of radio energy during athird time window based on the first durations and the first timequotas, and cause the plurality of radio entities to transmit radioenergy based on the second time quotas.
 29. The radio device of claim 1,wherein the second time quotas are different from the first time quotasby half a difference between a first duration of a first radio entityand a first time quota of the first radio entity.
 30. The radio deviceof claim 1, where a first portion of the plurality of radio entitieshave second quotas greater than the first time quotas, and a secondportion of the plurality of radio entities have second quotas less thanthe first time quotas.
 31. A radio device, comprising: a first radioentity and a second radio entity configured to transmit radio energy;and a controller communicatively coupled to the first radio entity andthe second radio entity and configured to assign a first time quota tothe first radio entity and the second radio entity for transmission ofradio energy during a first time window; cause the first radio entity totransmit radio energy for a first duration less than or equal to thefirst time quota; cause the second radio entity to transmit radio energyfor a second duration less than or equal to the first time quota; whenthe first duration is equal to the first time quota and the secondduration is less than the first time quota, assign a second time quotato the first radio entity and a third time quota to the second radioentity for transmission of radio energy during a second time window, thesecond time quota being greater than the first time quota and the thirdtime quota being less than the first time quota; and cause the firstradio entity to transmit radio energy based on the second time quota andthe second radio entity to transmit radio energy based on the third timequota during the second time window.
 32. The radio device of claim 31,wherein the controller is further configured to: when the first durationis less than the first time quota and the second duration is equal tothe first time quota, assign the third time quota to the first radioentity and the second time quota to the second radio entity.
 33. Theradio device of claim 31, wherein a difference between the second timequota and the first time quota is equal to half a difference between thesecond duration and the first time quota.
 34. The radio device of claim31, wherein a sum of the first duration and the second duration is lessthan or equal to a length of the first time window.
 35. The radio deviceof claim 31, wherein a sum of the second time quota and the third timequota is equal to a length of the second time window.
 36. The radiodevice of claim 31, wherein the controller is further configured to:when the first duration and the second duration are less than the firsttime quota, assign the first time quota to the first radio entity andthe second radio entity for transmission during the second time window.37. A radio device, comprising: a plurality of radio entities configuredto transmit radio energy; and a controller communicatively coupled tothe plurality of radio entities and configured to assign first timequotas to the plurality of the radio entities for transmission of radioenergy during a first time window, cause the plurality of radio entitiesto respectively transmit radio energy for first durations less than orequal to the first time quotas, assign second time quotas to theplurality of radio entities for a set of time windows different from thefirst time window based on first unused time quotas derived from thefirst durations and the first time quotas, where a sum of the secondtime quotas is equal to a sum of the first unused time quotas, and causethe plurality of radio entities to transmit radio energy based on thesecond time quotas.
 38. The radio device of claim 37, wherein thecontroller is further configured to calculate the first unused timequotas by subtracting the first durations from the first time quotas.39. The radio device of claim 37, wherein the second time quotas areproportionately allocated based on the first durations of the pluralityof radio entities.
 40. The radio device of claim 37, wherein the secondtime quotas are derived by evenly splitting the sum of the first unusedtime quotas between the plurality of radio entities.
 41. The radiodevice of claim 37, wherein the second time quotas are allocated basedon link qualities of the plurality of radio entities.
 42. The radiodevice of claim 41, wherein the link qualities are success rates of theplurality of radio entities for sending packets over a period of time.43. The radio device of claim 41, wherein the link qualities are basedon a modulation and coding scheme (MCS) used by the plurality of radioentities.
 44. The radio device of claim 37, wherein the first timequotas have durations equal to a duration of the first time window.